Motor having a braking function and used in linear actuator

ABSTRACT

A motor, which has a braking function and is used in a linear actuator includes a main body, a rotation shaft, a braking means and a stopping means. The rotation shaft penetrates the center of the main body. The braking means includes a braking ring and a helical ring. The braking ring includes a plurality of curved plates. The helical ring surrounds outer edges of the curved plates. Each curved plate is put on the outer periphery of the rotation shaft. The stopping means is disposed between the main body and the braking means for restricting the rotation of any of the curved plates. By this arrangement, a better braking and decelerating function can be achieved.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 13/429,378, filed on Mar. 25, 2012, and entitled “MOTOR HAVINGA BRAKING FUNCTION AND USED IN LINEAR ACTUATOR”. The entire disclosuresof the above application are all incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a motor used in a linear actuator, andin particular to a motor having a braking function and used in a linearactuator.

2. Description of Prior Art

Linear actuator employs a motor, a worm rod, a worm wheel and otherdriving elements to drive a lead screw to rotate. The lead screw drivesa telescope tube threadedly connected onto the lead screw to generate alinear extending action or retracting action. Since the structure andinstallation of the linear actuator are easier and more convenient thanthose of a pneumatic cylinder or a hydraulic cylinder, the linearactuator has been widely used in a sickbed, electric chair or otherplaces where extending and retracting actions are needed.

EP0662573B1 and WO2004-027290A2 disclose a linear actuator respectively.The linear actuator disclosed in EP0662573B1 includes a worm rod, a leadscrew, a worm wheel set fixed to one end of the lead screw. The wormwheel set comprises a worm wheel. A helical spring surrounds the outerperiphery of a cylindrical ring. In this way, the linear actuator can beobtained. In view of the problems of the EP0662573B1, the linearactuator disclosed in WO2004-027290A2 is provided with a heat-conductingelement for dissipating the heat generated by the frictional forcebetween the helical spring and the cylindrical ring.

However, in the conventional linear actuator, the helical spring isstationary, but the cylindrical ring is rotatable together with the wormwheel. Thus, heat is generated due to the friction force between thehelical spring and the cylindrical ring. The cylindrical ring is made ofplastic materials. The heat generated by the frictional force makes thetemperature of the cylindrical ring to increase and even melt. Or, thehelical spring may be worn quickly to reduce its lifetime. Only a linecontact is formed between the helical spring and the cylindrical ring togenerate a decelerating effect or braking effect. Thus, the contact areabetween the helical spring and the cylindrical ring is not large enoughto generate a sufficient decelerating effect or braking effect.

SUMMARY OF THE INVENTION

The present invention is to provide a motor having a braking functionand used in a linear actuator, in which a stopping means is provided toprevent the rotation of a braking ring. The helical ring constricts thebraking ring to brake a rotation shaft. In this way, a good braking anddecelerating effect can be achieved.

The present invention provides a motor having a braking function andused in a linear actuator, including a main body, a rotation shaft, abraking means and a stopping means. The rotation shaft penetrates thecenter of the main body. The braking means comprises a braking ring anda helical ring. The braking ring is constituted of a plurality of curvedplates. The helical ring surrounds the outer edge of each curved plate.Each curved plate is put on the outer periphery of the rotation shaft.The stopping means is disposed between the main body and the brakingmeans for restricting the rotation of any of the curved plates.

The present invention provides a motor having a braking function andused in a linear actuator, including a main body, a rotation shaft, abraking means and a stopping means. The rotation shaft penetrates thecenter of the main body. The braking means comprises a braking ring anda helical ring. The braking ring is provided with a groove. The helicalring surrounds the outer periphery of the braking ring. The braking ringis put on the outer periphery of the rotation shaft. The stopping meansis disposed between the main body and the braking means for restrictingthe rotation of the braking ring.

The present invention has advantageous features as follows. Since thewear of the helical spring is small, its lifetime is extended. Thecontact area between the braking ring and the rotation shaft is largeenough to generate a better braking and decelerating effect. The brakingmeans and the stopping means are disposed on the rotation shaft of thelinear actuator, so that only a small force is needed to generate abetter braking effect. When the telescopic tube retracts, a braking anddecelerating effect is obtained. Thus, the telescopic tube can be keptat a stable rate to lower or retract into an outer tube, thereby makinga user to feel more comfortable.

Further, the present invention has other advantages of simple structure,low cost, and small volume. With the rectangular structure of thebraking ring and/or one end of the helical spring being fixed, thebraking ring and the helical spring will not rotate relative to eachother, so that each curved plate can generate a better braking effect tothe rotation shaft.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is an exploded perspective view showing a first embodiment of thepresent invention;

FIG. 2 is an assembled view showing the external appearance of the firstembodiment of the present invention;

FIG. 3 is a partially cross-sectional view of FIG. 2;

FIG. 4 is a schematic view showing that the first embodiment of thepresent invention is used in a linear actuator;

FIG. 5 is an exploded perspective view showing a second embodiment ofthe present invention;

FIG. 6 is an assembled view showing the second embodiment of the presentinvention;

FIG. 7 is an exploded perspective view showing a third embodiment of thepresent invention;

FIG. 8 is an assembled view showing the external appearance of the thirdembodiment of the present invention;

FIG. 9 is a partially cross-sectional view of FIG. 8;

FIG. 10 is an exploded perspective view showing a fourth embodiment ofthe present invention;

FIG. 11 is a partially cross-sectional view of FIG. 10;

FIG. 12 is an exploded perspective view showing a fifth embodiment ofthe present invention;

FIG. 13 is an exploded perspective view showing a sixth embodiment ofthe present invention;

FIG. 14 is an assembled view showing the external appearance of thesixth embodiment of the present invention;

FIG. 15 is a partially cross-sectional view of FIG. 14;

FIG. 16 is an exploded perspective view showing a seventh embodiment ofthe present invention; and

FIG. 17 is an assembled view showing the external appearance of theseventh embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The detailed description and technical contents of the present inventionwill become apparent with the following detailed description accompaniedwith related drawings. It is noteworthy to point out that the drawingsis provided for the illustration purpose only, but not intended forlimiting the scope of the present invention.

Please refer to FIGS. 1 to 3. The present invention provides a motorhaving a braking function and used in a linear actuator. The motor 1includes a main body 10, a rotation shaft 20, a braking means 30, and astopping means 40.

The main body 10 has a cylindrical casing 11. The interior of the casing11 is provided with a stator, a rotor, a winding or the like (notshown). An end surface of the casing 11 is provided with an end cover12. The end cover 12 is provided with a plurality of threaded holes 121.

The rotation shaft 20 penetrates the center of the main body 10. Bothends of the rotation shaft 20 extend outwardly to be exposed to theoutside of the casing 11 and the end cover 12. One end of the rotationshaft 20 has a worm rod 21, and the other end of the rotation shaft 20near the end cover 12 is provided with a smooth section 22.

The braking means 30 comprises a braking ring 31 and a helical spring32. In the present embodiment, the braking ring 31 has a steppedcircular shape and is constituted of three curved plates 311. A slot 312is formed between any two adjacent curved plates 311. Each curved plate311 may be made of metallic or plastic materials for frictionallybraking the rotation shaft 20. The helical spring 32 surrounds andelastically presses the outer periphery of each curved plate 311. Thehelical spring 32 is a circular ring having a profile corresponding tothe profile of the braking ring 31. Each curved plate 311 is put on theouter periphery of the smooth section 22 of the rotation shaft 20. Thehelical spring 32 may be a right-hand helical spring. When the rotationshaft 20 rotates counterclockwise, the helical spring 32 and each curvedplate 311 generate a radial contraction. On the contrary, when therotation shaft 20 rotates clockwise, the helical spring 32 and eachcurved plate 311 generate a radial expansion.

The main body 10 further includes a shroud 41 and a screw element 42.With the screw element 42 penetrating the threaded hole 121, the shroud41 can be fixed to the end cover 12. The shroud 41 has an outer ring 411and an inner ring 412 connected to the outer ring 411 and formed insidethe outer ring 411. A groove 413 is formed between the outer ring 411and the inner ring 412. A stopping plate 414 protrudes inwardly from aninner wall surface of the inner ring 412. A portion of the helicalspring 32 is received in the groove 413 to be tightly put on the outerperiphery of the inner ring 412. The other portion of the helical spring32 is elastically put on the outer periphery of the large-diameter endof each curved plate 311. In the present embodiment, the stopping means40 includes the slot 312 formed between any two adjacent curved plates311 and the stopping plate 414 inserted into the slot 312 forrestricting the rotation of any curved plate 311.

Please refer to FIG. 4. The motor 1 of the present invention is mountedin a linear actuator 7. The linear actuator 7 includes a transmissionmeans 71, an outer tube 72, a telescopic tube 73, and other electricalelements or driving elements. The transmission means 71 comprises a leadscrew 711, a worm wheel 712, and a nut 713. One end of the outer tube 72is connected to the main body 10. The lead screw 711 is received insidethe outer tube 72. The worm wheel 712 is fixed to the lead screw 711 androtates together with the lead screw 711. One end of the telescopic tube73 is fixed to the nut 713, and the other end of the telescopic tube 73extends outside the outer tube 72. The nut 713 and the lead screw 711are in transmission connection with each other by means of threadedconnection. The motor 1 of the present invention is arranged on one sideof the end of the lead screw 711. The worm rod 21 of the rotation shaft20 is drivingly engaged with the worm wheel 712. By this arrangement,the linear actuator 7 is obtained.

In use, the rotation shaft 20 is driven by the internal elements of themain body 10 to rotate. When the worm wheel 712 is driven by the wormrod 21 to rotate counterclockwise, the lead screw 711 will drive thetelescopic tube 73 to retract into the outer tube 72. With one of thecurved plates 311 being stopped by the stopping plate 411 and thehelical spring 32 tightly constraining the outer periphery of thebraking ring 31, the helical spring 32 and each curved plate 311contract in a radial direction. At this time, the inner wall surface ofeach curved plate 311 rubs against the surface of the rotation shaft 20,thereby reducing the rotation speed of the rotation shaft 20 and thelead screw 711. In this way, when the linear actuator 7 is mounted in anelectric bed or electric chair, the retracting speed of the telescopictube 73 into the outer tube 72 can be made smaller, so that the userwill feel more comfortable when using such an electric bed or chair.

On the contrary, when the worm wheel 712 is driven by the worm rod 21 torotate clockwise, the lead screw 711 will drive the telescopic tube 73to extend out of the outer tube 72. Since the rotating direction of therotation shaft 20 is opposite to that of the winding direction of thehelical spring 32, the rotation shaft 20 drives each curved plate 311and the helical spring 32 to expand in a radial direction. At this time,each curved plate 311 is separately released from the surface of therotation shaft 20, thereby reducing the frictional force during therotation of the rotation shaft 20. In this way, the rotation shaft 20can rotate in the braking ring 31 easily without affecting thetransmission performance of the motor 1.

Please refer to FIGS. 5 and 6, which show the motor according to thesecond embodiment of the present invention. The difference between themotor 1 a of the second embodiment and the motor 1 of the firstembodiment lies in that: the braking ring 31 a has a rectangular shapeand is constituted of two curved plates 311 a. A slot 312 a is formedbetween any two adjacent curved plates 311 a. The helical spring 32 asurrounds and elastically presses the outer periphery of each curvedplate 311 a. The helical spring 32 a is a rectangular ring having anouter profile corresponding to that of the braking ring 31. Each curvedplate 311 a is put on an outer periphery of the smooth section 22 of therotation shaft 20. An end of the helical spring 32 a extends to form apositioning arm 321 a. In the present embodiment, the main body 10further includes a shroud 41 a and a screw element 42 a. The shroud 41 ahas an outer ring 411 a. A stopping plate 414 a protrudes inwardly froman inner wall surface of the outer ring 411 a. A groove 415 a is alsoformed on the inner wall surface of the outer ring 411 a. In the presentembodiment, the stopping means 40 a includes the slot 312 a formedbetween the two curved plates 311 a and the stopping plate 414 ainserted into the slot 312 a for restricting the rotation of any curvedplate 311 a. The positioning arm 321 a of the helical spring 32 a isinserted into the groove 415 a and positioned therein. With thenon-circular shape of the braking ring 31 a and one end of the helicalspring 32 a being fixed, the braking ring 31 a and the helical spring 32a cannot rotate relative to each other. In this way, each curved plate311 a can generate a better braking effect to the rotation shaft 20.

Please refer to FIGS. 7 to 9, which show the motor according to thethird embodiment of the present invention. The difference between themotor 1 b of the third embodiment and the motors of the previousembodiments lies in that: the braking ring 31 b is circular brakingring. The braking ring 31 b is provided with a slot 313 b in parallel toits central line (or axial line). The helical spring 32 b has a circularshape to surround the outer periphery of the braking ring 31 b. Thebraking ring 31 b is put on the outer periphery of the smooth section 22of the rotation shaft 20. An end of the helical spring 32 b extends toform a positioning arm 32 b. In the present embodiment, the stoppingmeans 40 b includes an insertion hole 44 b provided on the main body 10and a pin 43 b fixed on an end surface of the braking ring 31 b. The pin43 b is inserted into the insertion hole 44 b for restricting therotation of the braking ring 31 b. The main body 10 of the thirdembodiment further comprises a fixing element 13. The fixing element 13is fixed onto the end cover 12 via a screw element such as a screw. Thefixing element 13 is provided with a positioning hole 131 for allowingthe positioning arm 321 b of the helical spring 32 b to penetrate intothe positioning hole 131. In addition, the braking ring 31 b may beconfigured as a stepped circular ring like the first embodiment or arectangular ring like the second embodiment. Similarly, the helicalspring 32 b has an outer profile corresponding to that of the brakingring 31 b.

Please refer to FIGS. 10 and 11, which show the motor according to thefourth embodiment of the present invention. The difference between themotor 1 c of the fourth embodiment and the motors of the previousembodiments lies in that: the braking ring 31 c is a circular ringconstituted of three curved plates 311 c. In the present embodiment, thestopping means 40 c includes a slot 312 c formed between any twoadjacent curved plates 311 c and a pin 43 c fixed to the main body 10.The pin 43 c is inserted into the slot 312 c to restrict the rotation ofthe braking ring 31 c. The helical spring 32 c is also formed into acircular shape and surrounds the outer periphery of the braking ring 31c. An end of the helical spring 32 c extends to form a positioning arm321 c. The positioning arm 321 c of the helical spring 32 c is insertedinto the positioning hole 131 of the fixing element 13.

Please refer to FIG. 12, which show the motor according to the fifthembodiment of the present invention. The difference between the motor 1d of the fifth embodiment and the motors of the previous embodimentslies in that: the stopping means 40 d of the present embodiment includesa slot 312 d formed between any two adjacent curved plates 311 d and astopping block 45 d protruding from the end cover 12 of the main body10. The stopping block 45 d is inserted into the slot 312 d to restrictthe rotation of any braking ring 31 d. The helical spring 32 d is alsoformed into a circular shape and surrounds the outer periphery of thebraking ring 31 d.

Please refer to FIGS. 13 to 15, which show the motor according to thesixth embodiment of the present invention. The difference between themotor 1 e of the sixth embodiment and the motors of the previousembodiments lies in that: the main body 10 further comprises a shafttube 14. The shaft tube 14 is put on the distal end of the smoothsection 22 of the rotation shaft 20 and fixed in the end cover 12. Inthe present embodiment, the stopping means 40 e includes an insertionhole 44 e provided in the shaft tube 14 and a pin 43 e fixed to an endsurface of any curved plate 311 e. The pin 43 e is inserted into theinsertion hole 44 e to restrict the rotation of the braking ring 31 e.The interior of the end cover 12 is provided with an insertion trough122. The helical spring 32 e is formed into a circular shape to surroundthe outer periphery of the braking ring 31 e. An end of the helicalspring 32 e extends to form a positioning arm 321 e. The positioning arm321 e is inserted into the insertion trough 122 of the end cover 12.

Please refer to FIGS. 16 and 17, which show the motor according to theseventh embodiment of the present invention. The difference between themotor if of the seventh embodiment and the motors of the previousembodiment lies in that: one end of the casing 11 away from the endcover 12 is connected with a base 15. In the present embodiment, thestopping means 40 f includes a slot 312 f formed between any twoadjacent curved plates 311 f and a stopping block 43 f connected to thebase 15. The stopping block 43 f is inserted into the slot 312 f torestrict the rotation of the braking ring 31 f. In addition, theinterior of the base 15 is provided with a positioning trough 151. Anend of the helical spring 32 f extends to form a positioning arm 321 f.The positioning arm 321 f is inserted into the positioning trough 151 ofthe base 15.

Although the present invention has been described with reference to theforegoing preferred embodiments, it will be understood that theinvention is not limited to the details thereof. Various equivalentvariations and modifications can still occur to those skilled in thisart in view of the teachings of the present invention. Thus, all suchvariations and equivalent modifications are also embraced within thescope of the invention as defined in the appended claims.

What is claimed is:
 1. A motor having a braking function and used in alinear actuator, including: a main body; a rotation shaft penetratingthe center of the main body; a braking means comprising a braking ringand a helical ring, the braking ring being constituted of a plurality ofcurved plates, the helical ring surrounding an outer edge of each curvedplate, each curved plate being put on an outer periphery of the rotationshaft; and a stopping means disposed between the main body and thebraking means for restricting the rotation of any of the curved plates;wherein the main body comprises a base, a slot is formed between any twoadjacent curved plates, and the stopping means includes the slot and astopping block connected to the base and inserted into the slot.
 2. Themotor having a braking function and used in a linear actuator accordingto claim 1, wherein the main body is provided with a positioning trough,the helical spring extends to form a positioning arm, and thepositioning arm is inserted into the positioning trough for positioning.3. The motor having a braking function and used in a linear actuatoraccording to claim 1, wherein the braking ring is formed into a circularshape, and the helical spring is a circular ring for elasticallypressing the braking ring.
 4. The motor having a braking function andused in a linear actuator according to claim 1, wherein the braking ringis formed into a stepped circular shape, and the helical spring is acircular ring for elastically pressing the braking ring.